Lubricant compositions for direct injection engine

ABSTRACT

The invention is directed to a method for reducing low speed pre-ignition events in a spark-ignited direct injection internal combustion engine by supplying to the sump a lubricant composition which contains an oil of lubricating viscosity and an ashless dispersant. The ashless dispersant may be selected from succinimide compounds prepared from aliphatic or aromatic amines.

BACKGROUND OF THE INVENTION

The disclosed technology relates to lubricants for internal combustionengines, particularly those for spark-ignited direct injection engines.

Modern engine designs are being developed to improve fuel economywithout sacrificing performance or durability. Historically, gasolinewas port-fuel injected (PFI), that is, injected through the air intakeand entering the combustion chamber via the air intake valve. Gasolinedirect injection (GDI) involves direct injection of gasoline into thecombustion chamber.

In certain situations, the internal combustion engine may exhibitabnormal combustion. Abnormal combustion in a spark-initiated internalcombustion engine may be understood as an uncontrolled explosionoccurring in the combustion chamber as a result of ignition ofcombustible elements therein by a source other than the igniter.

Pre-ignition may be understood as an abnormal form of combustionresulting from ignition of the air-fuel mixture prior to ignition by theigniter. Anytime the air-fuel mixture in the combustion chamber isignited prior to ignition by the igniter, such may be understood aspre-ignition. It will also be understood that ignition events generallyincrease in likelihood as the air-fuel ratio becomes leaner. As such,one approach to preventing pre-ignition events in GDI engines has beento intentionally inject additional fuel (i.e., to overfuel), therebyadjusting the air-fuel ratio to a richer mixture that is less favorableto pre-ignition events. This approach has successfully treated LSPI, butmore current fuel efficiency and economy standards are causing enginemanufacturers to adopt leaner air-fuel mixtures, which leads to the needfor alternative approaches to preventing or reducing LSPI events.

Without being bound to a particular theory, traditionally, pre-ignitionhas occurred during high speed operation of an engine when a particularpoint within the combustion chamber of a cylinder may become hot enoughduring high speed operation of the engine to effectively function as aglow plug (e.g. overheated spark plug tip, overheated burr of metal) toprovide a source of ignition which causes the air-fuel mixture to ignitebefore ignition by the igniter. Such pre-ignition may be more commonlyreferred to as hot-spot pre-ignition, and may be inhibited by simplylocating the hot spot and eliminating it.

More recently, vehicle manufacturers have observed intermittent abnormalcombustion in their production of turbocharged gasoline engines,particularly at low speeds and medium-to-high loads. More particularly,when operating the engine at speeds less than or equal to 3,000 rpm andunder a load with a brake mean effective pressure (BMEP) of greater thanor equal to 10 bars, a condition which may be referred to as low-speedpre-ignition (LSPI) may occur in a very random and stochastic fashion.

The disclosed technology provides a method for reducing, inhibiting, oreven eliminating LSPI events in direct injection engines by operatingthe engines with a lubricant that contains a boron-containing ashlessdispersant. As used herein, the expression “boron-containing ashlessdispersant” is intended to include dispersants that are free of metalother than incidental amounts that may be incorporated from productionor synthesis (i.e. amounts less than 500 ppm by weight of thedispersant, or less than 300 ppm, or less than 100 ppm by weight of thedispersant).

SUMMARY OF THE INVENTION

The present invention provides a method for reducing low speedpre-ignition events in a spark-ignited direct injection internalcombustion engine comprising supplying to the sump a lubricantcomposition which contains an oil of lubricating viscosity and aboron-containing ashless dispersant. The boron-containing ashlessdispersant may be a polyisobutylene succinimide compound.

DETAILED DESCRIPTION

Various preferred features and embodiments will be described below byway of non-limiting illustration.

As indicated above, when operating the engine at speeds less than orequal to 3,000 rpm and under a load with a brake mean effective pressure(BMEP) of greater than or equal to 10 bars, a low-speed pre-ignition(LSPI) event may occur in the engine. A LSPI event may consist of one ormore LSPI combustion cycles, and generally consists of multiple LSPIcombustion cycles which occur in a consecutive fashion or alternatingfashion with normal combustion cycles in between. Without being bound toa particular theory, LSPI may result from a combustion of oildroplet(s), or a droplet(s) of oil-fuel mixture, or combinationsthereof, which may accumulate, for example, in the top land crevicesvolume of a piston, or the piston ring-land and ring-groove crevices.The lubricant oil may be transferred from below the oil control ring tothe piston top land area due to unusual piston ring movements. At lowspeed, high load conditions, in-cylinder pressures dynamics (compressionand firing pressures) may be considerably different from in-cylinderpressures at lower loads, particularly due to strongly retardedcombustion phasing and high boost and peak compression pressures whichcan influence ring motion dynamics.

At the foregoing loads, LSPI, which may be accompanied by subsequentdetonation and/or severe engine knock, can cause severe damage to theengine very quickly (often within 1 to 5 engine cycles). Engine knockmay occur with LSPI given that, after the normal spark from the igniteris provided, multiple flames may be present. The present invention aimsto provide a method for inhibiting or reducing LSPI events, the methodinvolving supplying to the engine a lubricant composition comprising aboron-containing ashless dispersant.

In one embodiment of the invention, the engine is operated at speedsbetween 500 rpm and 3000 rpm, or 800 rpm to 2800 rpm, or even 1000 rpmto 2600 rpm. Additionally, the engine may be operated with a brake meaneffective pressure of 10 bars to 30 bars, or 12 bars to 24 bars.

LSPI events, while comparatively uncommon, may be catastrophic innature. Hence drastic reduction or even elimination of LSPI eventsduring normal or sustained operation of a direct fuel injection engineis desirable. In one embodiment, the method of the invention is suchthat there are less than 20 LSPI events per 100,000 combustion events orless than 10 LSPI events per 100.000 combustion events. In oneembodiment, there may be less than 5 LSPI events per 100.000 combustionevents, less than 3 LSPI events per 100.000 combustion events; or theremay be 0 LSPI events per 100.000 combustion events. Fuel

The method of the present invention involves operating a spark-ignitedinternal combustion engine. In addition to the engine operatingconditions and the lubricant composition, the composition of the fuelmay impact LSPI events. In one embodiment, the fuel may comprise a fuelwhich is liquid at ambient temperature and is useful in fueling a sparkignited engine, a fuel which is gaseous at ambient temperatures, orcombinations thereof.

The liquid fuel is normally a liquid at ambient conditions e.g., roomtemperature (20 to 30° C.). The fuel can be a hydrocarbon fuel, anonhydrocarbon fuel, or a mixture thereof. The hydrocarbon fuel may be agasoline as defined by ASTM specification D4814. In an embodiment of theinvention the fuel is a gasoline, and in other embodiments the fuel is aleaded gasoline, or a nonleaded gasoline.

The non-hydrocarbon fuel can be an oxygen containing composition, oftenreferred to as an oxygenate, to include an alcohol, an ether, a ketone,an ester of a carboxylic acid, a nitroalkane, or a mixture thereof. Thenonhydrocarbon fuel can include for example methanol, ethanol, methylt-butyl ether, methyl ethyl ketone, transesterified oils and/or fatsfrom plants and animals such as rapeseed methyl ester and soybean methylester, and nitromethane. Mixtures of hydrocarbon and nonhydrocarbonfuels can include, for example, gasoline and methanol and/or ethanol. Inan embodiment of the invention, the liquid fuel is a mixture of gasolineand ethanol, wherein the ethanol content is at least 5 volume percent ofthe fuel composition, or at least 10 volume percent of the composition,or at least 15 volume percent, or 15 to 85 volume percent of thecomposition. In one embodiment, the liquid fuel contains less than 15%by volume ethanol content, less than 10% by volume ethanol content, lessthan 5% ethanol content by volume, or is substantially free of (i.e.less than 0.5% by volume) of ethanol.

In several embodiments of this invention, the fuel can have a sulfurcontent on a weight basis that is 5000 ppm or less, 1000 ppm or less,300 ppm or less, 200 ppm or less, 30 ppm or less, or 10 ppm or less. Inanother embodiment, the fuel can have a sulfur content on a weight basisof 1 to 100 ppm. In one embodiment, the fuel contains about 0 ppm toabout 1000 ppm, about 0 to about 500 ppm, about 0 to about 100 ppm,about 0 to about 50 ppm, about 0 to about 25 ppm, about 0 to about 10ppm, or about 0 to 5 ppm of alkali metals, alkaline earth metals,transition metals or mixtures thereof. In another embodiment the fuelcontains 1 to 10 ppm by weight of alkali metals, alkaline earth metals,transition metals or mixtures thereof.

The gaseous fuel is normally a gas at ambient conditions e.g., roomtemperature (20 to 30° C.). Suitable gas fuels include natural gas,liquefied petroleum gas (LPG), compressed natural gas (CNG), or mixturesthereof. In one embodiment, the engine is fueled with natural gas.

The fuel compositions of the present invention can further comprise oneor more performance additives. Performance additives can be added to afuel composition depending on several factors, including the type ofinternal combustion engine and the type of fuel being used in thatengine, the quality of the fuel, and the service conditions under whichthe engine is being operated. In some embodiments, the performanceadditives are free of nitrogen. In other embodiments, the additionalperformance additives may contain nitrogen.

The performance additives can include an antioxidant such as a hinderedphenol or derivative thereof and/or a diarylamine or derivative thereofa corrosion inhibitor such as an alkenylsuccinic acid; and/or adetergent/dispersant additive, such as a polyetheramine or nitrogencontaining detergent, including but not limited to polyisobutylene (PM)amine dispersants, Mannich detergents, succinimide dispersants, andtheir respective quaternary ammonium salts.

The performance additives may also include a cold flow improver, such asan esterified copolymer of maleic anhydride and styrene and/or acopolymer of ethylene and vinyl acetate; a foam inhibitor, such as asilicone fluid; a demulsifier such as a polyoxyalkylene and/or an alkylpolyether alcohol; a lubricity agent such as a fatty carboxylic acid,ester and/or amide derivatives of fatty carboxylic acids, or esterand/or amide derivatives of hydrocarbyl substituted succinic anhydrides;a metal deactivator, such as an aromatic triazole or derivative thereof,including but not limited to a benzotriazole such as tolytriazole;and/or a valve seat recession additive, such as an alkali metalsulfosuccinate salt. The additives may also include a biocide, anantistatic agent, a deicer, a fluidizer, such as a mineral oil and/or apoly(alpha-olefin) and/or a polyether, and a combustion improver, suchas an octane or cetane improver.

The fluidizer may be a polyetheramine or a polyether compound. Thepolyetheramine can be represented by the formula R[—OCH₂CH(R¹)]_(n)A,where R is a hydrocarbyl group, R¹ is selected from the group consistingof hydrogen, hydrocarbyl groups of 1 to 16 carbon atoms, and mixturesthereof, n is a number from 2 to about 50, and A is selected from thegroup consisting of —OCH₂CH₂CH₂NR²R² and —NR³R³, where each R² isindependently hydrogen or hydrocarbyl, and each R³ is independentlyhydrogen, hydrocarbyl or —[R⁴N(R⁵)]_(p)R⁶, where R⁴ is C₂-C₁₀ alkylene,R⁵ and R⁶ are independently hydrogen or hydrocarbyl, and p is a numberfrom 1-7.

The fluidizer can be a polyether, which can be represented by theformula R⁷O[CH₂CH(R⁸)O]_(q)H, where R⁷ is a hydrocarbyl group, R⁸ isselected from the group consisting of hydrogen, hydrocarbyl groups of 1to 16 carbon atoms, and mixtures thereof, and q is a number from 2 toabout 50. The fluidizer can be a hydrocarbyl-terminatedpoly-(oxyalkylene) aminocarbamate as described U.S. Pat. No. 5,503,644.The fluidizer can be an alkoxylate, wherein the alkoxylate can comprise:(i) a polyether containing two or more ester terminal groups; (ii) apolyether containing one or more ester groups and one or more terminalether groups; or (iii) a polyether containing one or more ester groupsand one or more terminal amino groups, wherein a terminal group isdefined as a group located within five connecting carbon or oxygen atomsfrom the end of the polymer. Connecting is defined as the sum of theconnecting carbon and oxygen atoms in the polymer or end group.

The performance additives which may be present in the fuel additivecompositions and fuel compositions of the present invention also includedi-ester, di-amide, ester-amide, and ester-imide friction modifiersprepared by reacting a dicarboxylic acid (such as tartaric acid) and/ora tricarboxylic acid (such as citric acid), with an amine and/oralcohol, optionally in the presence of a known esterification catalyst.These friction modifiers often derived from tartaric acid, citric acid,or derivatives thereof may be derived from amines and/or alcohols thatare branched so that the friction modifier itself has significantamounts of branched hydrocarbyl groups present within it structure.Examples of suitable branched alcohols used to prepare these frictionmodifiers include 2-ethylhexanol, isotridecanol, Guerbet alcohols, ormixtures thereof.

In different embodiments the fuel composition may have a composition asdescribed in the following table:

Embodiments (ppm) Additive A C D Detergent/ 0 to 2500  25 to 150  500 to2500 dispersant Fluidizer 0 to 5000  1 to 250 3000 to 5000 Demulsifier 0to 50  0.5 to 5    1 to 25 Corrosion 0 to 200   .5 to 10  20 to 200Inhibitor Antioxidant 0 to 1000  5 to 125  500 to 1000 Friction 0 to600   50 to 175 100 to 750 Modifier Fuel Balance to 100% Balance to 100%Balance to 100%

Oil of Lubricating Viscosity

The lubricating composition comprises an oil of lubricating viscosity.Such oils include natural and synthetic oils, oil derived fromhydrocracking, hydrogenation, and hydrofinishing, unrefined, refined,re-refined oils or mixtures thereof. A more detailed description ofunrefined, refined and re-refined oils is provided in InternationalPublication WO2008/147704, paragraphs [0054] to [0056] (a similardisclosure is provided in US Patent Publication 2010/0197536, see [0072]to [0073]). A more detailed description of natural and syntheticlubricating oils is described in paragraphs [0058] to [0059]respectively of WO2008/147704 (a similar disclosure is provided in USPatent Publication 2010/0197536, see [0075] to [0076]). Synthetic oilsmay also be produced by Fischer-Tropsch reactions and typically may behydroisomerized Fischer-Tropsch hydrocarbons or waxes. In oneembodiment, oils may be prepared by a Fischer-Tropsch gas-to-liquidsynthetic procedure as well as other gas-to-liquid oils.

Oils of lubricating viscosity may also be defined as specified in theApril 2008 version of “Appendix E—API Base Oil InterchangeabilityGuidelines for Passenger Car Motor Oils and Diesel Engine Oils”, section1.3 Sub-heading 1.3. “Base Stock Categories”. The API Guidelines arealso summarized in U.S. Pat. No. 7,285,516 (see column 11, line 64 tocolumn 12, line 10). In one embodiment, the oil of lubricating viscositymay be an API Group II, Group III, or Group IV oil, or mixtures thereof.The five base oil groups are as follows:

Base Oil Category Sulfur (%) Saturates (%) Viscosity Index Group I >0.03and/or <90 80 to 120 Group II ≤0.03 and ≥90 80 to 120 Group III ≤0.03and ≥90 ≥120 Group IV All polyalphaolefins (PAO) Group V All others notincluded in Groups I, II, III, or IV

The amount of the oil of lubricating viscosity present is typically thebalance remaining after subtracting from 100 weight % (wt %) the sum ofthe amount of the compound of the invention and the other performanceadditives.

The lubricating composition may be in the form of a concentrate and/or afully formulated lubricant. If the lubricating composition of theinvention (comprising the additives disclosed herein) is in the form ofa concentrate which may be combined with additional oil to form, inwhole or in part, a finished lubricant, the ratio of the of theseadditives to the oil of lubricating viscosity and/or to diluent oilinclude the ranges of 1:99 to 99:1 by weight, or 80:20 to 10:90 byweight.

In one embodiment, the base oil has a kinematic viscosity at 100° C.from 2 mm²/s (centiStokes—cSt) to 16 mm²/s, from 3 mm²/s to 10 mm²/s, oreven from 4 mm²/s to 8 mm²/s.

The ability of a base oil to act as a solvent (i.e. solvency) may be acontributing factor in increasing the frequency of LSPI events duringoperation of a direct fuel-injected engine. Base oil solvency may bemeasured as the ability of un-additized base oil to act as a solvent forpolar constituents. In general, base oil solvency decreases as the baseoil group moves from Group Ito Group IV (PAO). That is, solvency of baseoil may be ranked as follows for oil of a given kinematic viscosity:Group I>Group II>Group II>Group IV. Base oil solvency also decreases asthe viscosity increases within a base oil group; base oil of lowviscosity tends to have better solvency than similar base oil of higherviscosity. Base oil solvency may be measured by aniline point (ASTMD611).

In one embodiment, the base oil comprises at least 30 wt % of Group IIor Group III base oil. In another embodiment, the base oil comprises atleast 60 weight % of Group II or Group III base oil, or at least 80 wt %of Group II or Group III base oil. In one embodiment, the lubricantcomposition comprises less than 20 wt % of Group IV (i.e.polyalphaolefin) base oil. In another embodiment, the base oil comprisesless than 10 wt % of Group IV base oil. In one embodiment, thelubricating composition is substantially free of (i.e. contains lessthan 0.5 wt %) of Group IV base oil.

Ester base fluids, which are characterized as Group V oils, have highlevels of solvency as a result of their polar nature. Addition of lowlevels (typically less than 10 wt %) of ester to a lubricatingcomposition may significantly increase the resulting solvency of thebase oil mixture. Esters may be broadly grouped into two categories:synthetic and natural. An ester base fluid would have a kinematicviscosity at 100° C. suitable for use in an engine oil lubricant, suchas between 2 cSt and 30 cSt, or from 3 cSt to 20 cSt, or even from 4 cStto 12 cSt.

Synthetic esters may comprise esters of dicarboxylic acids (e.g.,phthalic acid, succinic acid, alkyl succinic acids and alkenyl succinicacids, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaricacid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonicacids, and alkenyl malonic acids) with any of variety of monohydricalcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol,2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, andpropylene glycol). Specific examples of these esters include dibutyladipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctylsebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate,didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester oflinoleic acid dimer, and the complex ester formed by reacting one moleof sebacic acid with two moles of tetraethylene glycol and two moles of2-ethylhexanoic acid. Other synthetic esters include those made from C5to C12 monocarboxylic acids and polyols and polyol ethers such asneopentyl glycol, trimethylolpropane, pentaerythritol,dipentaerythritol, and tripentaerythritol. Esters can also be monoestersof mono-carboxylic acids and monohydric alcohols.

Natural (or bio-derived) esters refer to materials derived from arenewable biological resource, organism, or entity, distinct frommaterials derived from petroleum or equivalent raw materials. Naturalesters include fatty acid triglycerides, hydrolyzed or partiallyhydrolyzed triglycerides, or transesterified triglyceride esters, suchas fatty acid methyl ester (or FAME). Suitable triglycerides include,but are not limited to, palm oil, soybean oil, sunflower oil, rapeseedoil, olive oil, linseed oil, and related materials. Other sources oftriglycerides include, but are not limited to, algae, animal tallow, andzooplankton. Methods for producing bio-lubricants from naturaltriglycerides are described in, e.g., United States Patent Publication2011/0009300A1.

In one embodiment, the lubricating composition comprises at least 2 wt %of an ester base fluid. In one embodiment the lubricating composition ofthe invention comprises at least 4 wt % of an ester base fluid, or atleast 7 wt % of an ester base fluid, or even at least 10 wt % of anester base fluid.

Boron-Containing Ashless Dispersant

Boron-containing ashless dispersants, are well known in the field oflubricants. Ashless dispersants are so-called because, as supplied, theydo not contain metal and thus do not normally contribute to sulfated ashwhen added to a lubricant. However, they may, interact with ambientmetals once they are added to a lubricant which includes ametal-containing species. Ashless dispersants are characterized by apolar group attached to a relatively high molecular weight hydrocarbonchain. Typical ashless dispersants include N-substituted long chainalkenyl succinimides, having a variety of chemical structures, includingthose represented by Formula (I):

where each R¹ is independently an alkyl group, frequently apolyisobutylene group with a molecular weight (M_(n)) of 500-5000 basedon the polyisobutylene precursor, and R² are alkylene groups, commonlyethylene (C₂H₄) groups. Succinimides of the invention may bemono-succinimides (i.e. a succinimide as in Formula (I) with a terminal—NH₂ group in place of the second succinimide), bis-succinimides (as inFormula (I) above), or mixtures thereof.

Such molecules are commonly derived from reaction of an alkenylacylating agent with a polyamine, and a wide variety of linkages betweenthe two moieties is possible beside the simple imide structure shownabove, including a variety of amides and quaternary ammonium salts. Inthe above Formula (I), the amine portion is shown as an alkylenepolyamine, although other aliphatic and aromatic mono- and polyaminesmay also be used. Also, a variety of modes of linkage of the le groupsonto the imide structure are possible, including various cycliclinkages. The ratio of the carbonyl groups of the acylating agent to thenitrogen atoms of the amine may be 1:0.5 to 1:3, and in other instances1:1 to 1:2.75 or 1:1.5 to 1:2.5. Succinimide dispersants are more fullydescribed in U.S. Pat. Nos. 4,234,435 and 3,172,892 and in EP 0355895.

In certain embodiments, the dispersant is prepared by a process thatinvolves the presence of small amounts of chlorine or other halogen, asdescribed in U.S. Pat. No. 7,615,521 (see, e.g., col. 4, lines 18-60 andpreparative example A). Such dispersants typically have some carbocyclicstructures in the attachment of the hydrocarbyl substituent to theacidic or amidic “head” group. In other embodiments, the dispersant isprepared by a thermal process involving an “ene” reaction, without theuse of any chlorine or other halogen, as described in U.S. Pat. No.7,615,521; dispersants made in this manner are often derived from highvinylidene (i.e. greater than 50% terminal vinylidene) polyisobutylene(See col. 4, line 61 to col. 5, line 30 and preparative example B). Suchdispersants typically do not contain the above-described carbocyclicstructures at the point of attachment. In certain embodiments, thedispersant is prepared by free radical catalyzed polymerization ofhigh-vinylidene polyisobutylene with an ethylenically unsaturatedacylating agent, as described in U.S. Pat. No. 8,067,347.

Dispersants may be derived from, as the polyolefin, high vinylidenepolyisobutylene, that is, having greater than 50, 70, or 75% terminalvinylidene groups (α and β isomers). In certain embodiments, thesuccinimide dispersant may be prepared by the direct alkylation route.In other embodiments it may comprise a mixture of direct alkylation andchlorine-route dispersants.

Reaction of ethylenically unsaturated acylating agent (preferably maleicanhydride) with a polyolefin to form the acylated polyalkenyl precursormay be carried out such that one or more acylating agents are attachedto the polyalkenyl group. When the acylating agent is maleic anhydride,this is described as succination ratio. Dispersants prepared from thestoichiometric reaction of maleic anhydride and a suitable polyolefinmay be referred to as mono-succinated. Dispersants prepared from a 2:1ratio of maleic anhydride to polyolefin may be referred to asdi-succinated. The succination ratio of the dispersant may be 1 to 2, or1.2 to 1.85, or 1.35 to 1.75 succinate moieties per mol of polyolefin.

Suitable dispersants for use in the compositions of the presentinvention include succinimide dispersants. In one embodiment, thedispersant may be present as a single dispersant. In one embodiment, thedispersant may be present as a mixture of two or three differentdispersants, wherein at least one may be a succinimide dispersant.

The succinimide dispersant may be a derivative of an aliphaticpolyamine, or mixtures thereof. The aliphatic polyamine may be aliphaticpolyamine such as an ethylenepolyamine, a propylenepolyamine, abutylenepolyamine, or mixtures thereof. In one embodiment, the aliphaticpolyamine may be ethylenepolyamine. In one embodiment the aliphaticpolyamine may be selected from the group consisting of ethylenediamine,diethylenetriamine, triethylenetetramine, tetraethylenepentamine,pentaethylene-hexamine, polyamine still bottoms, and mixtures thereof.

The succinimide dispersant may be a derivative of an aromatic amine, anaromatic polyamine, or mixtures thereof. The aromatic amine may be4-aminodiphenylamine (ADPA) (also known as N-phenylphenylenediamine),derivatives of ADPA (as described in United States Patent Publications2011/0306528 and 2010/0298185), a nitroaniline, an aminocarbazole, anamino-indazolinone, an aminopyrimidine, 4-(4-nitrophenylazo)aniline, orcombinations thereof. In one embodiment, the dispersant is derivative ofan aromatic amine wherein the aromatic amine has at least threenon-continuous aromatic rings.

The succinimide dispersant may be a derivative of a polyether amine orpolyether polyamine. Typical polyether amine compounds contain at leastone ether unit and will be chain terminated with at least one aminemoiety. The polyether polyamines can be based on polymers derived fromC₂-C₆ epoxides such as ethylene oxide, propylene oxide, and butyleneoxide. Examples of polyether polyamines are sold under the Jeffamine®brand and are commercially available from Hunstman Corporation locatedin Houston, Tex.

Another class of ashless dispersant is high molecular weight esters.These materials are similar to the above-described succinimides exceptthat they may be seen as having been prepared by reaction of ahydrocarbyl acylating agent and a polyhydric aliphatic alcohol such asglycerol, pentaerythritol, or sorbitol. Such materials are described inmore detail in U.S. Pat. No. 3,381,022. Aromatic succinate esters mayalso be prepared as described in United States Patent Publication2010/0286414.

A succinic-based dispersant (succinimide, succinamide, succinic ester,and mixtures thereof) may be formed by reacting maleic anhydride or areactive equivalent thereof, such as an acid or ester, with ahydrocarbon chain by any method such as those disclosed above (e.g.,chlorine-based process or thermal process). Other acids or equivalentsthereof may be used in place of the maleic anhydride. These includefumaric acid, itaconic acid, itaconic anhydride, citraconic acid,citaconic anhydride, and cinnamic acid as well as other ethylenicallyunsaturated acids such as acrylic or methacrylic acid; and theirreactive equivalents.

Another class of ashless dispersant is Mannich bases. These arematerials which are formed by the condensation of a higher molecularweight, alkyl substituted phenol, an alkylene polyamine, and an aldehydesuch as formaldehyde. Such materials may have the general structure asrepresented by Formula (II)

(including a variety of isomers and the like) and are described in moredetail in U.S. Pat. No. 3,634,515.

Another class of ashless dispersants include dispersants comprising aquaternary ammonium salt. Quaternary ammonium salts include the reactionproduct of: (i) a compound comprising at least one tertiary amino group;and (ii) a quaternizing agent suitable for converting the tertiary aminogroup of compound (i) to a quaternary nitrogen. Examples of suitablequaternary ammonium salts include (i) imide quaternary ammonium salts,(ii) Mannich quaternary ammonium salts, (iii) polyalkene substitutedamine quaternary ammonium salts, (iv) amide quaternary ammonium salts,(v) ester quaternary ammonium salts, (vi) polyester quaternary ammoniumsalts, or (vii) any combination thereof.

These various types of quaternary ammonium salts may be prepared in anynumber of ways but generally are prepared by reacting a non-quaternizednitrogen-containing compound with a quaternizing agent. Each of thedifferent types of quaternary ammonium salts described uses a differentnon-quaternized nitrogen-containing compound in its preparation, butgenerally the non-quaternized nitrogen-containing compound contains atertiary nitrogen capable of being quaternized (or a primary orsecondary nitrogen atom that can be alkylated to a tertiary nitrogenthat can then be quaternized) and a hydrocarbyl substituent group. Thepreparation and use of quaternized ammonium dispersants is described indetail in U.S. Pat. Nos. 7,951,211 and 7,906,470.

The boron-containing dispersant may be any of the above-mentionedashless dispersants, preferably polyisobutenylsuccinimide dispersants,which are reacted with a borating (or boronating) agent, resulting inincorporation or association of boron or a boron-containing moiety withthe ashless dispersant.

Boron-containing dispersants (i.e. borated dispersants) may be known tothe skilled person and may be prepared by reacting a borating agent,such as boric acid, with a polyalkenyl succinimide, preferably apolyisobutenyl succinimide. Other suitable borating agents includetrialkyl borate esters and alkali metal borates. The borated dispersantmay have a carbonyl to nitrogen ratio of 1:1 to 1:5, or 1:1 to 1:4, or1:1.3 to 1:3 or 1:1.5 to 1:2, or 1:1.4 to 1:0.6.

The borated dispersant may additionally be post-treated by otherconventional methods by a reaction with any of a variety of agents.Among these are urea, thiourea, dimercaptothiadiazoles, carbondisulfide, aldehydes, ketones, carboxylic acids, hydrocarbon-substitutedsuccinic anhydrides, maleic anhydride, nitriles, epoxides, andphosphorus compounds.

The boron-containing dispersant may also exhibit basicity, as measuredby Total Base Number (TBN). TBN may be determined by ASTM D2896. Thiswill particularly be the case if the dispersant is prepared with anamine, such as a polyamine, and the amine contains one or more aminogroups that have not reacted with acidic groups of the dispersant. Insome embodiments, the TBN of the dispersant may be 1 to 110, or 5 to 50,or 10 to 40 or 30 to 70. In some embodiments, however, the dispersantmay not exhibit basicity (that is, have a TBN of 0 or nearly 0). In oneembodiment the dispersant has a TBN of zero as measured by D2896. Suchcould be the case if no basic nitrogen is present on the dispersant

The boron-containing dispersant may be present at 0.01 wt % to 20 wt %,or 0.1 wt % to 15 wt %, or 0.1 wt % to 10 wt %, or 0.5 wt % to 8 wt %,or 1.0 wt % to 6.5 wt %, or 0.5 wt % to 2.2 wt % of the lubricatingcomposition.

The boron-containing dispersant may be present in an amount to deliverboron to the composition at 15 ppm to 2000 ppm, or 25 ppm to 1000 ppm,or 40 ppm to 600 ppm, or 80 ppm to 350 ppm.

Other Performance Additives

The compositions of the invention may optionally comprise one or moreadditional performance additives. These additional performance additivesmay include one or more metal deactivators, viscosity modifiers,detergents, friction modifiers, antiwear agents, corrosion inhibitors,boron-free dispersants, dispersant viscosity modifiers, extreme pressureagents, antioxidants, foam inhibitors, demulsifiers, pour pointdepressants, seal swelling agents, and any combination or mixturethereof. Typically, fully-formulated lubricating oil will contain one ormore of these performance additives, and often a package of multipleperformance additives.

In one embodiment, the invention provides a lubricating compositionfurther comprising an antiwear agent, a dispersant viscosity modifier, afriction modifier, a viscosity modifier, an antioxidant, an overbaseddetergent, a boron-free dispersant, or a combination thereof, where eachof the additives listed may be a mixture of two or more of that type ofadditive. In one embodiment, the invention provides a lubricatingcomposition further comprising an antiwear agent, a dispersant viscositymodifier, a friction modifier, a viscosity modifier (typically an olefincopolymer such as an ethylene-propylene copolymer), an antioxidant(including phenolic and aminic antioxidants), an overbased detergent(including overbased sulfonates and phenates), or a combination thereof,where each of the additives listed may be a mixture of two or more ofthat type of additive.

In one embodiment, the invention provides a lubricating compositionfurther comprising a boron-free ashless dispersant. The boron-freedispersant may be the same or different than the borated dispersant ofthe invention. In one embodiment, the boron-free dispersant may bepresent in the lubricant in an amount 0.1 weight percent to 5 weightpercent of the composition, or 0.25 to 2.4 weight percent, or 1.0 to 3.0weight percent of the composition. In one embodiment, the lubricatingcomposition may include one or more boron-containing dispersants and oneor more boron-free dispersants, wherein the total amount of dispersantmay be 0.01 wt % to 20 wt %, or 0.1 wt % to 15 wt %, or 0.1 wt % to 10wt %, or 0.5 wt % to 8 wt % , or 1.0 wt % to 6.5 wt %, or 0.5 wt % to2.2 wt % of the lubricating composition and wherein the ratio of borateddispersant to boron-free dispersant may be 1:10 to 10:1 (weight:weight)or 1:5 to 3:1 or 1:3 to 2:1.

Another additive is an antiwear agent. Examples of anti-wear agentsinclude phosphorus-containing antiwear/extreme pressure agents such asmetal thiophosphates, phosphoric acid esters and salts thereof,phosphorus-containing carboxylic acids, esters, ethers, and amides, andphosphites. In certain embodiments a phosphorus antiwear agent may bepresent in an amount to deliver 0.01 to 0.2 or 0.015 to 0.15 or 0.02 to0.1 or 0.025 to 0.08 percent phosphorus. Often the antiwear agent is azinc dialkyldithiophosphate (ZDP).

Zinc dialkyldithiophosphates may be described as primary zincdialkyldithiophosphates or as secondary zinc dialkyldithiophosphates,depending on the structure of the alcohol used in its preparation. Insome embodiments the compositions of the invention include primary zincdialkyldithiophosphates. In some embodiments the compositions of theinvention include secondary zinc dialkyldithiophosphates. In someembodiments the compositions of the invention include a mixture ofprimary and secondary zinc dialkyldithiophosphates. In some embodimentscomponent (b) is a mixture of primary and secondary zincdialkyldithiophosphates where the ratio of primary zincdialkyldithiophosphates to secondary zinc dialkyldithiophosphates (one aweight basis) is at least 1:1, or even at least 1:1.2, or even at least1:1.5 or 1:2, or 1:10. In some embodiments, component (b) is a mixtureof primary and secondary zinc dialkyldithiophosphates that is at least50 percent by weight primary, or even at least 60, 70, 80, or even 90percent by weight primary. In some embodiments component (b) is free ofprimary zinc dialkyldithiophosphates.

The phosphorus antiwear agent may be present at 0 wt % to 3 wt %, or 0.1wt % to 1.5 wt %, or 0.5 wt % to 0.9 wt % of the lubricatingcomposition.

In one embodiment, the invention provides a lubricating compositionwhich further comprises ashless antioxidant. Ashless antioxidants maycomprise one or more of arylamines, diarylamines, alkylated arylamines,alkylated diaryl amines, phenols, hindered phenols, sulfurized olefins,or mixtures thereof. In one embodiment the lubricating compositionincludes an antioxidant, or mixtures thereof. The antioxidant may bepresent at 0 wt % to 15 wt %, or 0.1 wt % to 10 wt %, or 0.5 wt % to 5wt %, or 0.5 wt % to 3 wt %, or 0.3 wt % to 1.5 wt % of the lubricatingcomposition.

The diarylamine or alkylated diarylamine may be a phenyl-α-naphthylamine(PANA), an alkylated diphenylamine, or an alkylated phenylnapthylamine,or mixtures thereof. The alkylated diphenylamine may includedi-nonylated diphenylamine, nonyl diphenylamine, octyl diphenylamine,di-octylated diphenylamine, di-decylated diphenylamine, decyldiphenylamine and mixtures thereof. In one embodiment, the diphenylaminemay include nonyl diphenylamine, dinonyl diphenylamine, octyldiphenylamine, dioctyl diphenylamine, or mixtures thereof. In oneembodiment the alkylated diphenylamine may include nonyl diphenylamine,or dinonyl diphenylamine. The alkylated diarylamine may include octyl,di-octyl, nonyl, di-nonyl, decyl or di-decyl phenylnapthylamines.

The diarylamine antioxidant of the invention may be present on a weightbasis of the lubrication composition at 0.1% to 10%, 0.35% to 5%, oreven 0.5% to 2%.

The phenolic antioxidant may be a simple alkyl phenol, a hinderedphenol, or coupled phenolic compounds.

The hindered phenol antioxidant often contains a secondary butyl and/ora tertiary butyl group as a sterically hindering group. The phenol groupmay be further substituted with a hydrocarbyl group (typically linear orbranched alkyl) and/or a bridging group linking to a second aromaticgroup. Examples of suitable hindered phenol antioxidants include2,6-di-tert-butylphenol, 4-methyl-2,6-di-tert-butylphenol,4-ethyl-2,6-di-tert-butylphenol, 4-propyl-2,6-di-tert-butylphenol or4-butyl-2,6-di-tert-butylphenol, 4-dodecyl-2,6-di-tert-butylphenol, orbutyl 3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoate. In one embodiment,the hindered phenol antioxidant may be an ester and may include, e.g.,Irganox™ L-135 from Ciba.

Coupled phenols often contain two alkylphenols coupled with alkylenegroups to form bisphenol compounds. Examples of suitable coupled phenolcompounds include 4,4′-methylene bis-(2,6-di-tert-butyl phenol),4-methyl-2,6-di-tert-butylphenol, 2,2′-bis-(6-t-butyl-4-heptylphenol);4,4′-bis(2,6-di-t-butyl phenol),2,2′-methylenebis(4-methyl-6-t-butylphenol), and 2,2′-methylenebis(4-ethyl-6-t-butylphenol).

Phenols of the invention also include polyhydric aromatic compounds andtheir derivatives. Examples of suitable polyhydric aromatic compoundsinclude esters and amides of gallic acid, 2,5-dihydroxybenzoic acid,2,6-dihydroxybenzoic acid, 1,4-dihydroxy-2-naphthoic acid,3,5-dihydroxynaphthoic acid, 3,7-dihydroxy naphthoic acid, and mixturesthereof.

In one embodiment, the phenolic antioxidant comprises a hindered phenol.In another embodiment the hindered phenol is derived from2,6-ditertbutyl phenol.

In one embodiment, the lubricating composition of the inventioncomprises a phenolic antioxidant in a range of 0.01 wt % to 5 wt %, or0.1 wt % to 4 wt %, or 0.2 wt % to 3 wt %, or 0.5 wt % to 2 wt % of thelubricating composition.

Sulfurized olefins are well known commercial materials, and those whichare substantially nitrogen-free, that is, not containing nitrogenfunctionality, are readily available. The olefinic compounds which maybe sulfurized are diverse in nature. They contain at least one olefinicdouble bond, which is defined as a non-aromatic double bond; that is,one connecting two aliphatic carbon atoms. These materials generallyhave sulfide linkages having 1 to 10 sulfur atoms, for instance, 1 to 4,or 1 or 2.

Ashless antioxidants may be used separately or in combination. In oneembodiment of the invention, two or more different antioxidants are usedin combination, such that there is at least 0.1 weight percent of eachof the at least two antioxidants and wherein the combined amount of theashless antioxidants is 0.5 to 5 weight percent. In one embodiment,there may be at least 0.25 to 3 weight percent of each ashlessantioxidant.

In one embodiment, the invention provides a lubricating compositionfurther comprising a molybdenum compound. The molybdenum compound may beselected from the group consisting of molybdenumdialkyldithiophosphates, molybdenum dithiocarbamates, amine salts ofmolybdenum compounds, and mixtures thereof. The molybdenum compound mayprovide the lubricating composition with 0 to 1000 ppm, or 5 to 1000ppm, or 10 to 750 ppm, or 5 ppm to 300 ppm, or 20 ppm to 250 ppm ofmolybdenum.

In one embodiment, the lubricating composition of the invention furthercomprises a dispersant viscosity modifier. The dispersant viscositymodifier may be present at 0 wt % to 5 wt %, or 0 wt % to 4 wt %, or0.05 wt % to 2 wt % of the lubricating composition.

Suitable dispersant viscosity modifiers include functionalizedpolyolefins, for example, ethylene-propylene copolymers that have beenfunctionalized with an acylating agent such as maleic anhydride and anamine; polymethacrylates functionalized with an amine, or esterifiedstyrene-maleic anhydride copolymers reacted with an amine. More detaileddescription of dispersant viscosity modifiers are disclosed inInternational Publication WO2006/015130 or U.S. Pat. Nos. 4,863,623;6,107,257; 6,107,258; and 6,117,825. In one embodiment, the dispersantviscosity modifier may include those described in U.S. Pat. No.4,863,623 (see column 2, line 15 to column 3, line 52) or inInternational Publication WO2006/015130 (see page 2, paragraph [0008]and preparative examples are described at paragraphs [0065] to [0073]).

In one embodiment, the invention provides a lubricating compositionfurther comprising a metal-containing detergent. The metal-containingdetergent may be an overbased detergent. Overbased detergents otherwisereferred to as overbased or superbased salts are characterized by ametal content in excess of that which would be necessary forneutralization according to the stoichiometry of the metal and theparticular acidic organic compound reacted with the metal. The overbaseddetergent may be selected from the group consisting of non-sulfurcontaining phenates, sulfur containing phenates, sulfonates,salixarates, salicylates, and mixtures thereof.

The metal-containing detergent may also include “hybrid” detergentsformed with mixed surfactant systems including phenate and/or sulfonatecomponents, e.g. phenate/salicylates, sulfonate/phenates,sulfonate/salicylates, sulfonates/phenates/salicylates, as described,for example, in U.S. Pat. Nos. 6,429,178; 6,429,179; 6,153,565; and6,281,179. Where, for example, a hybrid sulfonate/phenate detergent isemployed, the hybrid detergent would be considered equivalent to amountsof distinct phenate and sulfonate detergents introducing like amounts ofphenate and sulfonate soaps, respectively.

The overbased metal-containing detergent may be sodium salts, calciumsalts, magnesium salts, or mixtures thereof of the phenates,sulfur-containing phenates, sulfonates, salixarates and salicylates.Overbased phenates and salicylates typically have a total base number of180 to 450 TBN. Overbased sulfonates typically have a total base numberof 250 to 600, or 300 to 500. Overbased detergents are known in the art.In one embodiment, the sulfonate detergent may be predominantly a linearalkylbenzene sulfonate detergent having a metal ratio of at least 8 asis described in paragraphs [0026] to [0037] of US Patent Publication2005065045 (and granted as U.S. Pat. No. 7,407,919). The linearalkylbenzene sulfonate detergent may be particularly useful forassisting in improving fuel economy. The linear alkyl group may beattached to the benzene ring anywhere along the linear chain of thealkyl group, but often in the 2, 3 or 4 position of the linear chain,and in some instances, predominantly in the 2 position, resulting in thelinear alkylbenzene sulfonate detergent. Overbased detergents are knownin the art. The overbased detergent may be present at 0 wt % to 15 wt %,or 0.1 wt % to 10 wt %, or 0.2 wt % to 8 wt %, or 0.2 wt % to 3 wt %.For example, in a heavy duty diesel engine, the detergent may be presentat 2 wt % to 3 wt % of the lubricating composition. For a passenger carengine, the detergent may be present at 0.2 wt % to 1 wt % of thelubricating composition.

Metal-containing detergents contribute sulfated ash to a lubricatingcomposition. Sulfated ash may be determined by ASTM D874. In oneembodiment, the lubricating composition of the invention comprises ametal-containing detergent in an amount to deliver at least 0.4 weightpercent sulfated ash to the total composition. In another embodiment,the metal-containing detergent is present in an amount to deliver atleast 0.6 weight percent sulfated ash, or at least 0.75 weight percentsulfated ash, or even at least 0.9 weight percent sulfated ash to thelubricating composition.

In one embodiment, the invention provides a lubricating compositionfurther comprising a friction modifier. Examples of friction modifiersinclude long chain fatty acid derivatives of amines, fatty esters, orepoxides; fatty imidazolines such as condensation products of carboxylicacids and polyalkylene-polyamines; amine salts of alkylphosphoric acids;fatty alkyl tartrates; fatty alkyl tartrimides; or fatty alkyltartramides. The term fatty, as used herein, can mean having a C8-22linear alkyl group.

Friction modifiers may also encompass materials such as sulfurized fattycompounds and olefins, molybdenum dialkyldithiophosphates, molybdenumdithiocarbamates, sunflower oil or monoester of a polyol and analiphatic carboxylic acid.

In one embodiment the friction modifier may be selected from the groupconsisting of long chain fatty acid derivatives of amines, long chainfatty esters, or long chain fatty epoxides; fatty imidazolines; aminesalts of alkylphosphoric acids; fatty alkyl tartrates; fatty alkyltartrimides; and fatty alkyl tartramides. The friction modifier may bepresent at 0 wt % to 6 wt %, or 0.05 wt % to 4 wt %, or 0.1 wt % to 2 wt% of the lubricating composition.

In one embodiment, the friction modifier may be a long chain fatty acidester. In another embodiment the long chain fatty acid ester may be amono-ester or a diester or a mixture thereof, and in another embodimentthe long chain fatty acid ester may be a triglyceride.

Other performance additives such as corrosion inhibitors include thosedescribed in paragraphs 5 to 8 of U.S. application Ser. No. 05/038,319,published as WO2006/047486, octyl octanamide, condensation products ofdodecenyl succinic acid or anhydride and a fatty acid such as oleic acidwith a polyamine. In one embodiment, the corrosion inhibitors includethe Synalox® (a registered trademark of The Dow Chemical Company)corrosion inhibitor. The Synalox® corrosion inhibitor may be ahomopolymer or copolymer of propylene oxide. The Synalox® corrosioninhibitor is described in more detail in a product brochure with FormNo. 118-01453-0702 AMS, published by The Dow Chemical Company. Theproduct brochure is entitled “SYNALOX Lubricants, High-PerformancePolyglycols for Demanding Applications”.

The lubricating composition may further include metal deactivators,including derivatives of benzotriazoles (typically tolyltriazole),dimercaptothiadiazole derivatives, 1,2,4-triazoles, benzimidazoles,2-alkyldithiobenzimidazoles, or 2-alkyldithio-benzothiazoles; foaminhibitors, including copolymers of ethyl acrylate and2-ethylhexylacrylate and copolymers of ethyl acrylate and2-ethylhexylacrylate and vinyl acetate; demulsifiers including trialkylphosphates, polyethylene glycols, polyethylene oxides, polypropyleneoxides and (ethylene oxide-propylene oxide) polymers; and pour pointdepressants, including esters of maleic anhydride-styrene,polymethacrylates, polyacrylates or polyacrylamides.

Pour point depressants that may be useful in the compositions of theinvention further include polyalphaolefins, esters of maleicanhydride-styrene, poly(meth)acrylates, polyacrylates orpolyacrylamides.

In different embodiments the lubricating composition may have acomposition as described in the following table:

Embodiments (wt %) Additive A B C Borated Dispersant 0.05 to 12   0.75to 8   0.5 to 6   of the invention Boron-free Dispersant 0.0 to 5   0.15to 4   0.5 to 2   Antioxidant 0.05 to 1   0.2 to 3   0.5 to 2  Dispersant Viscosity 0 or 0 or 0.05 to 2   Modifier 0.05 to 5   0.05 to4   Overbased Detergent 0 or 0.1 to 10  0.2 to 8   0.05 to 15   AntiwearAgent 0 or 0.1 to 10  0.3 to 5   0.05 to 15   Friction Modifier 0 or0.05 to 4   0.1 to 2   0.05 to 6   Viscosity Modifier 0 or 0.5 to 8   1to 6 0.05 to 10   Any Other Performance 0 or 0 or 0 or Additive 0.05 to10   0.05 to 8   0.05 to 6   Oil of Lubricating Balance to Balance toBalance to Viscosity 100% 100% 100%

The present invention provides a surprising ability to prevent damage toan engine in operation due to pre-ignition events resulting from directgasoline injection into the combustion chamber. This is accomplishedwhile maintaining fuel economy performance, low sulfated ash levels, andother limitations, required by increasingly stringent governmentregulations.

INDUSTRIAL APPLICATION

As described above, the invention provides for a method of lubricatingan internal combustion engine comprising supplying to the internalcombustion engine a lubricating composition as disclosed herein.Generally, the lubricant is added to the lubricating system of theinternal combustion engine, which then delivers the lubricatingcomposition to the critical parts of the engine, during its operation,that require lubrication.

The lubricating compositions described above may be utilized in aninternal combustion engine. The engine components may have a surface ofsteel or aluminum (typically a surface of steel), and may also be coatedfor example with a diamond-like carbon (DLC) coating.

An aluminum surface may be comprised of an aluminum alloy that may be aeutectic or hyper-eutectic aluminum alloy (such as those derived fromaluminum silicates, aluminum oxides, or other ceramic materials). Thealuminum surface may be present on a cylinder bore, cylinder block, orpiston ring having an aluminum alloy, or aluminum composite.

The internal combustion engine may be fitted with an emission controlsystem or a turbocharger. Examples of the emission control systeminclude diesel particulate filters (DPF), or systems employing selectivecatalytic reduction (SCR).

The internal combustion engine of the present invention is distinct froma gas turbine. In an internal combustion engine, individual combustionevents translate from a linear reciprocating force into a rotationaltorque through the rod and crankshaft. In contrast, in a gas turbine(which may also be referred to as a jet engine) a continuous combustionprocess generates a rotational torque continuously without translation,and can also develop thrust at the exhaust outlet. These differences inoperation conditions of a gas turbine and internal combustion engineresult in different operating environments and stresses.

The lubricant composition for an internal combustion engine may besuitable for any engine lubricant irrespective of the sulfur, phosphorusor sulfated ash (ASTM D-874) content. The sulfur content of the engineoil lubricant may be 1 wt % or less, or 0.8 wt % or less, or 0.5 wt % orless, or 0.3 wt % or less. In one embodiment, the sulfur content may bein the range of 0.001 wt % to 0.5 wt %, or 0.01 wt % to 0.3 wt %. Thephosphorus content may be 0.2 wt % or less, or 0.12 wt % or less, or 0.1wt % or less, or 0.085 wt % or less, or 0.08 wt % or less, or even 0.06wt % or less, 0.055 wt % or less, or 0.05 wt % or less. In oneembodiment the phosphorus content may be 100 ppm to 1000 ppm, or 200 ppmto 600 ppm. The total sulfated ash content may be 2 wt % or less, or 1.5wt % or less, or 1.1 wt % or less, or 1 wt % or less, or 0.8 wt % orless, or 0.5 wt % or less, or 0.4 wt % or less. In one embodiment, thesulfated ash content may be 0.05 wt % to 0.9 wt %, or 0.1 wt % to 0.2 wt% or to 0.45 wt %.

In one embodiment, the lubricating composition may be an engine oil,wherein the lubricating composition may be characterized as having atleast one of (i) a sulfur content of 0.5 wt % or less, (ii) a phosphoruscontent of 0.1 wt % or less, (iii) a sulfated ash content of 1.5 wt % orless, or combinations thereof.

EXAMPLES

The invention will be further illustrated by the following examples,which set forth particularly advantageous embodiments. While theexamples are provided to illustrate the invention, they are not intendedto limit it.

Lubricating Compositions

A series of 5W-20 engine lubricants in Group II base oil of lubricatingviscosity are prepared containing the ashless dispersant additivesdescribed above as well as conventional additives including polymericviscosity modifier, overbased detergents, antioxidants (combination ofphenolic ester and diarylamine), zinc dialkyldithiophosphate (ZDDP), aswell as other performance additives as set forth in Table 1. Thephosphorus, sulfur and ash contents of each of the examples are alsopresented in the Table in part to show that each example has a similaramount of these materials and so provide a proper comparison between thecomparative and invention examples.

TABLE 1 Lubricating Oil Composition Formulations COMP EX1 INV EX2 INVEX3 INV EX4 INV EX5 INV EX6 Group III Base Oil Balance to = 100%Dispersant 1² 0.8 1.2 2.0 3.6 2.4 Dispersant 2³ 4.6 Ashless Antioxidant⁴2.0 0.725 1.4 2.0 2.18 4.0 Ca Detergent⁵ 0.75 0.37 1.13 0.06 1.11 0.74Ca Phenate⁶ 0 0 0 1.4 0 0 Na Sulfonate 0.18 0.09 0 0 0.26 0.18 ZDDP 0.760.4 0.7 0.45 1.1 0.76 VI Improver 1.0 1.0 2.1 1.1 1.0 0.55 AdditionalAdditives⁷ 1.0 0.85 1.4 0.58 2.1 2.0 % Phosphorus 0.076 0.038 0.0600.046 0.11 0.076 % Calcium 0.168 0.084 0.234 0.123 0.251 0.168 % Sodium0.049 0.024 0 0 0.073 0.049 % Molybdenum (ppm) 0 46 0 0 140 90 TBN 10.83.84 7.75 6.1 11.5 10.8 % Ash 0.9 0.44 0.9 0.50 1.31 0.88 ¹All amountsshown above are in weight percent and are on an oil-free basis unlessotherwise noted ²PIBsuccinimide Dispersant, prepared from 2000 Mnpolyisobutylene, sucinated in a conventional chlorine process to form a“mid-succan” with 1.3-1.6 succination ratio, and aminated withpolyethylene polyamines; TBN = 28 ³PIBsuccinimide Dispersant, preparedfrom 1500 Mn high vinylidene polyisobutylene, thermally succinated, andaminated with polyethylene polyamines; TBN = 20 ⁴Combination ofdiarylamine and hindered phenol antioxidants ⁵Ca Detergent is one ormore overbased calcium alkylbenzene sulfonic acid with TBN at least 300and metal ratio at least 10 ⁶Ca Phenate is 145 TBN calcium phenate ⁷TheAdditional Additives used in the examples includes a dispersant, and anantifoam agent, and includes some amount of diluent oil. The sameAdditive package is used in each of the examples

TABLE 2 Lubricating Oil Composition Formulations¹ EX7 EX8 EX9 EX10 EX11EX12 Viscosity Grade 5W-30 10W-30 Base Oil Group III (Balance to = 100%)Group II (Balance to 100%) Borated Dispersant² 1 1 1.5 Boron-freeDispersant³ 2 2.7 2.0 Boron-free Dispersant⁴ 2.35 2.35 2.35 CaSulfonate⁵ 2.78 2.78 0.29 0.22 0.22 0.32 Ca Sulfonate⁶ 0.9 0.9 0.9 MgDetergent⁷ 2.92 0.81 0.81 0.71 Calcium Phenate 0.71 DVM Booster 0.250.58 0.58 Hindered phenol 0.25 0.5 05 1 1 1 Diarylamine 0.5 0.9 0.351.75 0 0 Sulfurized Olefin 0.9 0.2 0.25 0.25 0.25 ZDDP 0.32 0.32 0.320.77 0.77 0.77 VI Improver 0.6 0.6 0.4 0.05 0.05 0.08 AdditionalAdditives⁹ 0.46 0.73 0.36 0.16 0.16 0.16 % Phosphorus 0.03 0.03 0.030.075 0.074 0.079 % Calcium 0.71 0.71 0.064 0.128 0.126 0.150 %Magnesium 0 0 0.42 0.075 0.072 0.062 % Boron (ppm) 0 0 0 96 101 148 ¹Allamounts shown above are in weight percent and are on an oil-free basisunless otherwise noted. ²Borated Polyisobutylene (Mn 2300) basedsuccinimide dispersant prepared with ethylene polyamines (TBN 498); 1.0%Boron, Boron:Nitrogen 0.4:1 ³Polyisobutylene (Mn 2300) based succinimidedispersant prepared with ethylene polyamines (TBN = 28) ⁴Polyisobutylene(Mn 2300) based succinimide dispersant prepared with a mixture ofethylene polyamines and polyaromatic polyamines ⁵Ca Detergent is one ormore overbased calcium alkylbenzene sulfonic acid with TBN at least 300and metal ratio at least 10 ⁶High substrate calcium alkylbenzenesulfonate (metal ratio 2.8) ⁷Combination of overbased magnesiumalkylbenzene sulfonate and magnesium sulfur-free phenate detergents⁸Calcium overbased sulfur-coupled alkylphenol detergent ⁹The AdditionalAdditives used in the examples may include friction modifiers, pourpoint depressants, anti-foam agents, corrosion inhibitors, TBN boosters,and includes some amount of diluent oil.

Testing

Low Speed Pre-Ignition events are measured in two engines, a Ford 2.0 LEcoboost engine and a GM 2.0 L Ecotec. Both of these engines areturbocharged gasoline direct injection (GDI) engines. The Ford Ecoboostengine is operated in two stages. In the first stage, the engine isoperated at 1500 rpm and 14.4 bar brake mean effective pressure (BMEP).During the second stage, the engine is operated at 1750 rpm and 17.0 barBMEP. The engine is run for 25,000 combustion cycles in each stage, andLSPI events are counted.

The GM Ecotec engine is operated at 2000 rpm and 22.0 bar BMEP with anoil sump temperature of 100 oC. The test consists of nine phases of15,000 combustion cycles with each phase separated by an idle period.Thus combustion events are counted over 135,000 combustion cycles.

LSPI events are determined by monitoring peak cylinder pressure (PP) andmass fraction burn (MFB) of the fuel charge in the cylinder. When bothcriteria are met, it is determined that an LSPI event has occurred. Thethreshold for peak cylinder pressure is typically 9,000 to 10,000 kPa.The threshold for MFB is typically such that at least 2% of the fuelcharge is burned late, i.e. 5.5 degrees After Top Dead Center (ATDC).LSPI events can be reported as events per 100,000 combustion cycles,events per cycle, and/or combustion cycles per event.

TABLE 4 GM Ecotec LSPI Testing EX7 EX8 EX9 EX10 EX11 EX12 PP Events 1826 4 0 0 0 MFB Events 21 29 3 0 0 0 Total Events 18 26 3 0 0 0 TotalCycles 135,000 135,000 135,000 135,000 135,000 135,000 Ave. PP 18,90018,400 17370 6663 6675 6554 Events per 13.3 19.2 2.2 0 0 0 100,000cycles Cycles per 7500 5192 45000 N/A N/A N/A event

The data indicates that addition of borated dispersant to a formulation,especially a formulation already containing a magnesium detergent,results in significant reduction of LSPI events.

It is known that some of the materials described above may interact inthe final formulation, so that the components of the final formulationmay be different from those that are initially added. The productsformed thereby, including the products formed upon employing lubricantcomposition of the present invention in its intended use, may not besusceptible of easy description. Nevertheless, all such modificationsand reaction products are included within the scope of the presentinvention; the present invention encompasses lubricant compositionprepared by admixing the components described above.

Each of the documents referred to above is incorporated herein byreference, as is the priority document and all related applications, ifany, which this application claims the benefit of Except in theExamples, or where otherwise explicitly indicated, all numericalquantities in this description specifying amounts of materials, reactionconditions, molecular weights, number of carbon atoms, and the like, areto be understood as modified by the word “about”. Unless otherwiseindicated, each chemical or composition referred to herein should beinterpreted as being a commercial grade material which may contain theisomers, by-products, derivatives, and other such materials which arenormally understood to be present in the commercial grade. However, theamount of each chemical component is presented exclusive of any solventor diluent oil, which may be customarily present in the commercialmaterial, unless otherwise indicated. It is to be understood that theupper and lower amount, range, and ratio limits set forth herein may beindependently combined. Similarly, the ranges and amounts for eachelement of the invention may be used together with ranges or amounts forany of the other elements.

As used herein, the term “hydrocarbyl substituent” or “hydrocarbylgroup” is used in its ordinary sense, which is well-known to thoseskilled in the art. Specifically, it refers to a group having a carbonatom directly attached to the remainder of the molecule and havingpredominantly hydrocarbon character. Examples of hydrocarbyl groupsinclude:

-   -   (i) hydrocarbon substituents, that is, aliphatic (e.g., alkyl or        alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl)        substituents, and aromatic-, aliphatic-, and        alicyclic-substituted aromatic substituents, as well as cyclic        substituents wherein the ring is completed through another        portion of the molecule (e.g., two substituents together form a        ring);    -   (ii) substituted hydrocarbon substituents, that is, substituents        containing non-hydrocarbon groups which, in the context of this        invention, do not alter the predominantly hydrocarbon nature of        the substituent (e.g., halo (especially chloro and fluoro),        hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and        sulphoxy);    -   (iii) hetero substituents, that is, substituents which, while        having a predominantly hydrocarbon character, in the context of        this invention, contain other than carbon in a ring or chain        otherwise composed of carbon atoms.

Heteroatoms include sulfur, oxygen, nitrogen, and encompass substituentsas pyridyl, furyl, thienyl and imidazolyl. In general, no more than two,preferably no more than one, non-hydrocarbon substituent will be presentfor every ten carbon atoms in the hydrocarbyl group; typically, therewill be no non-hydrocarbon substituents in the hydrocarbyl group.

While the invention has been explained in relation to its preferredembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims.

What is claimed:
 1. A method for reducing low speed pre-ignition eventsin a spark-ignited direct injection internal combustion enginecomprising supplying to the engine a lubricant composition comprising: abase oil of lubricating viscosity; 0.5 to 2.2 wt % of a boratedpolyisobutylene based succinimide dispersant; 0.1 to 3 wt % of at leastone ashless antioxidant; and 0.2 to 1 wt % of a magnesium detergentselected from one or more of an overbased alkylbenzene sulfonatedetergent and a magnesium sulfur-free phenate detergent.
 2. The methodof claim 1, wherein the engine is operated under a load with a brakemean effective pressure (BMEP) of greater than or equal to 10 bars. 3.The method of claim 1, wherein the engine is operated at speeds lessthan or equal to 3,000 rpm.
 4. The method of claim 1, wherein the engineis fueled with a liquid hydrocarbon fuel, a liquid non-hydrocarbon fuel,or mixtures thereof.
 5. The method of claim 4, wherein the engine isfueled by natural gas, liquefied petroleum gas (LPG), compressed naturalgas (CNG), or mixtures thereof.
 6. The method of claim 1, wherein thepolyisobutylene succinimide compound is prepared from an aminecomprising one or more of aliphatic polyamines, aromatic amines,polyether amines, and mixtures thereof.
 7. The method of claim 1,further comprising from 0.1 to 5 wt % of a boron-free ashlessdispersant.
 8. The method of claim 7, wherein the boron-free ashlessdispersant is a polyisobutylene succinimide dispersant prepared from apolyisobutylene having an average number molecular weight (M_(n)) offrom 500 to
 5000. 9. The method of claim 1, wherein the at least oneashless antioxidant is a sulfurized olefin.
 10. The method of claim 1,wherein the at least one ashless antioxidant includes two or moreantioxidants where each antioxidant is present in the lubricatingcomposition in an amount of at least 0.1 wt %.
 11. The method of claim10, wherein the total amount of antioxidant present in the lubricatingcomposition is from 0.5 to 5 wt %.
 12. The method of claim 11, whereineach antioxidant is present in an amount of 0.25 to 3 wt %.
 13. Themethod of claim 1, wherein the lubricant composition further comprisesat least one other additive selected from a metal containing overbaseddetergent, a phosphorus-containing anti-wear additive, a frictionmodifier, and a polymeric viscosity modifier.
 14. The method of claim 1,wherein the lubricating composition comprises at least 50 weight % ofGroup II base oil, Group III base oil, or mixtures thereof.